This invention relates to a multiple-needle tufting machine, and more particularly to a clamp insert for tufting elements in a narrow gauge tufting machine.
The conventional hook bars for multiple-needle tufting machines are long bars extending transversely of the machine below the needles and the base fabric. A conventional cut-pile hook bar has deeply elongated slots formed through its bottom face and uniformly spaced for receiving the hooks which cooperate with the needles to form loops in the yarns carried by the needle. For a narrow gauge, multiple-needle tufting machine, the looper slots in the hook bar must be formed close together. The proximity of the spacing of the looper slots is limited by the thinness of the walls between the slots. Conventional loopers or hooks are held in their respective slots by individual set screws which are threaded into each slot and engage the opposed walls or lands of the slots. Thus, the thinness of the walls is further limited by the diameters of the set screws. Moreover, the threaded movement of the set screws tends to expand and warp the slot walls or lands.
One solution to spacing the looper slots closer together in a narrow gauge tufting machine is disclosed in the prior U.S. Pat. No. 3,635,177, issued Jan. 18, 1972 to Larry P. Gable et al for NARROW GAUGE HOOK BAR FOR TUFTING MACHINE. The Gable patent discloses a hook bar having uniformly spaced, but staggered, looper slots formed alternately in the front and rear faces of the hook bar. Thus, the staggered front and rear slots receive two transverse rows of staggered hooks or loopers for cooperation with corresponding staggered needles. However, the hook bar disclosed in the Gable patent was primarily designed for a looper apparatus for forming narrow gauge loop pile.
Another method of spacing the hook slots closer together in a narrow gauge tufting machine is disclosed in U.S. Pat. No. 4,067,270 of HOYT E. SHORT for "NARROW GAUGE CUT PILE TUFTING APPARATUS", in which the needles are staggered and the loopers are made quite thin and flexible for bending and veering around each of the corresponding staggered needles.
A further solution for spacing loopers and hook slots closer together in a narrow gauge machine is disclosed in U.S. Pat. No. 4,158,399 of HOYT E. SHORT, issued June 19, 1979, for "NARROW GAUGE CUT PILE LOOPER APPARATUS." In this narrow gauge cut-pile tufting machine, the needles are staggered and the slots are formed in the front and rear faces of the hook bar. However, the slots are designed to extend along the top of the hook bar to receive and reinforce the elongated body portions of the specially constructed looper hooks.
Another type of hook bar or looper apparatus for mounting a plurality of looper hooks close together in order to provide a more narrow gauge for multiple-needle tufting machines, is disclosed in U.S. Pat. No. 4,217,837, of Max M. Beasley et al, issued Aug. 19, 1980, for "FINE GAUGE LOOPER APPARATUS FOR IN-LINE TUFTING MACHINE." In this looper apparatus, the hook slots are formed in an insert bar received in the front face of the hook bar, and the looper hooks are held in position by a plurality of clamp members threadedly secured to the hook block and against the front body portions of the looper hooks. The hook bars are made in the form of elongated modules which are mounted end-to-end and each of the clamp members is adapted to secure a limited number of hooks upon the hook bar module.
In recent times, a plurality of thin hooks have been mounted securely and precisely in a hook bar by casting the metal forming the hook bar around the pre-set hooks. However, although strength, rigidity, and precision are attained, nevertheless, an entire cast module of hooks must be discarded if only a single hook becomes defective.
Modular hook bars including gauge inserts for receiving the loop hooks are disclosed in the co-pending application of Kenneth C. Curtis, et al, Ser. No. 447,974, filed Jan. 26, 1983, for "MODULAR HOOK BAR WITH GAUGE INSERT FOR TUFTING MACHINE." This application is assigned to TUFTCO CORPORATION, the same assignee of the instant application. Even though the above hook bar structure with the gauge inserts operates advantageously, nevertheless, each looper hook is still retained in position in its gauge insert by a set screw. There must be one set screw for each loop hook. Thus, the fineness of the gauge is limited to a certain extent by the thickness or diameter of each set screw. Moreover, the fineness of the gauge is also limited by the number and thickness of the individual slots, each of which receives a separate looper hook.
Conventional needle bars for multiple needle tufting machines are long, continuous, solid bars extending transversely of the machine above the base fabric for the entire width of the fabric to be tufted. A conventional needle bar includes a plurality of needle holes extending vertically through the needle bar and desirably parallel to each other, uniformly spaced at the desired needle gauge. Each needle is inserted through the needle hole in the bottom of the needle bar so that each needle extends substantially the full height, if not the full height, of the needle bar. The needles are secured in position in their respective needle holes by transverse set screws.
The conventional needle bar has always been of one of the most difficult parts of a tufting machine to manufacture, since the numerous needle holes must be drilled very accurately in the long needle bar. It is extremely difficult to control the path of the drill bit through a needle bar which is usually 7/8" in depth or height. In the drilling operation, the drill bit often "leads off" in one direction or another at an angle to the vertical. Accordingly, such angular drill holes through the needle bar will not be parallel to each other. Therefore, the elongated needles extending through the angular needle holes would be "off gauge" where the needle holes are not drilled in truly vertical paths. The longer the needle, therefore, the greater the gauge error.
The "lead off" of the drilling paths for each needle hole may be caused by various factors. A drill bit which is not accurately ground, or a drill bit being forced too rapidly into the metal of the needle bar, or a drill bit striking the more dense or harder portion of the metal in the needle bar, can cause the drill bit to deflect from its truly vertical course.
Once the drilling of the conventional needle bar has commenced, it is not possible to determine the path of the drill bit until it emerges from the opposite side of the needle bar. In a multiple needle tufting machine having several hundred needles, the gauge errors between the needles caused by the inaccurate drilling of the needle holes can create considerable problems.
Not only does the drilling of the needle holes involve maintaining accurate control of the drilling paths of the drill bits, but occasionally a drill bit will break off in the drilled needle hole, and the broken drill bit cannot be removed without damaging the needle bar.
All of the above problems in the drilling of the needle holes can result in a needle bar which cannot be used and which must be discarded or scrapped.
Normally, it takes approximately 40 man-hours to drill all of the required needle holes in a conventional needle bar of a multiple needle tufting machine.
Some of the above problems have been overcome by a segmental needle bar, such as that disclosed in the co-pending patent application of JERRY T. GREEN et al, Ser. No. 464,410, filed Feb. 7, 1983, for "SEGMENTAL NEEDLE BAR FOR MULTIPLE NEEDLE TUFTING MACHINE", assigned to the same assignee, TUFTCO CORPORATION. However, in the above-described segmental needle bar, there must be one set screw for each needle.